(Not Applicable)
At a shooting scene, the police frequently are confronted with a number of witnesses with conflicting stories. A rapid, reliable test for determining which of these witnesses had recently shot a gun is very useful for differentiating suspects from witnesses.
One technique used by investigators is to detect chemicals unique to a gunshot on the skin of a suspect. Gun cartridges contain a primer that ignites when it is subjected to high impact pressure by a firing pin of the gun, and a propellant (such as gunpowder) that burns when ignited by the primer. Although most of the propellant burns to produce gases that propel the bullet out the barrel, traces of unburned propellant are dispersed around the surface of the gun where they come into contact with the hands, arms, clothes, or face of the operator. The gases also propel particles of the unburned propellant onto the hands, clothes, arms, or face of the operator. If the aforementioned test detects trace chemicals from the gunpowder on a person, there is a strong presumption that person recently shot a gun, or was in close proximity to someone who did.
In one prior art field test, the paraffin test, the hands of the suspect are coated with a layer of melted paraffin. When the paraffin cools and hardens, the casts are removed and treated with a diphenylamine solution, which will color nitrates from nitroglycerine or nitrocellulose on the cast. This is a test that must be done in a laboratory, as the wax must be kept hot and melted prior to use. The chemistry of this test is discussed by Ervin Jungreis, xe2x80x9cSpot Test Analysis, Clinical, Environmental, Forensic, and Geochemical Applications, 2nd ed.xe2x80x9d, John Wiley and Sons, NY, 1997, Chapter 4.
The solution for this test is prepared by diluting 10 mL of concentrated sulfuric acid with 2 mL of distilled water, and then adding 0.05 grams of diphenylamine (DPA) and stirring until the DPA is dissolved. DPA is a colorless to gray solid crystal chemical that is used in rubber processing chemicals, pharmaceuticals, dyes, and as an additive for petroleum and plastic products. It has as synonyms N-phenylbenzenamine, phenylaminobenzene, big dipper, N-phenylaniline, scaldip, and anilinobenzene. It has a formula of C12H11N, and it reacts with strong acids (which is why the sulfuric acid is only slightly diluted). Both the acid and the DPA are toxic to skin, which explains why this accurate and court-approved test is conventionally performed on paraffin casts in a laboratory environment.
For another test, the skin of the suspect is swabbed with dilute hydrochloric acid. Chemicals that change colors in the presence of antimony, barium, or lead, which are other components of gun residue, are then applied to the swab.
Expray(trademark) is an aerosol field test kit where a surface is wiped with a special test paper and sprayed with a series of chemicals. Each spray results in a color change on the paper if various explosive components are present. This test kit is not effective for gunshot residues.
A paper by John Baytos, xe2x80x9cField Spot-Test Kit for Explosivesxe2x80x9d, Los Alamos National Laboratories, LA-12071-MS, July 1991, discloses a field kit that uses a sealed box containing swabs, chemicals, a UV light for detecting color changes, a sealable plastic envelope for protection of the swab for delivery to a laboratory for more thorough analysis. This kit is intended to detect explosives but will not detect gunshot residue. The chemical bottles and UV lamp are not as rugged as is desired for use by a law enforcement officer at a crime scene.
The aforementioned systems are not routinely used by police investigators who typically swab suspects with dilute nitric acid, seal the swab in a plastic container for transportation to a laboratory, and analyze with a scanning electron microscope (SEM) to identify the shape of inorganic particles and their chemical elements. These SEM tests are very accurate, quite expensive, and not capable of giving on-the-spot results.
Other related technology to this invention is noted:
M. Child et al., U.S. Pat. No. 5,766,962, issued Jun. 16, 1998, describes a rigid plastic container having an internal chamber containing a fluid, a place for a specimen to be placed in the container, and a viewing port. After a sample of material to be tested (such as feces) is placed in the container, the internal chamber is ruptured so fluid flows through an internal channel past the specimen to a diagnostic strip that changes color under the viewing port.
J. R. Riese, U.S. Pat. No. 4,637,061, issued Jan. 13, 1987, discloses a dual-chamber specimen and transport container. A fixative or transport solution is sealed in a lower chamber. In use, a specimen is placed in the upper chamber and the seal between chambers is undone, allowing the solution to contact the specimen. The particular seal in the ""061 patent is a pair of interlocking members which make a reusable seal. Other similar packages are noted in the Background Art of the ""061 patent.
It is very desirable to have an easy-to-use kit that does not involve applying a chemical to the test subject and that would provide the police at the scene with a reliable indication of which person should be treated as a suspect.
It is an object of this invention to provide a field kit for the detection of gunshot residue that is easily transportable by police, and which may quickly be used to provide an indication on the scene of whether or not a possible suspect may have recently shot a gun. To achieve the foregoing and other objects, and in accordance with the purpose of the present invention, as embodied and broadly described herein, the invention is a field test kit for detecting gunshot residue including a swab capable of being wiped by an operator upon a surface to pick up gunshot residue; a reagent for reacting with gunshot residue on said swab to provide a rapid, visible indication of the residue; and a container having first and second compartments, the second compartment containing the reagent. The first compartment has an opening for permitting the swab to be moved into the first compartment, and the opening is then sealed to prevent contamination of the device and to keep the reagent in the container. A barrier keeps the reagent out of the first compartment, but the barrier is opened by the operator to allow the reagent to pass into the first compartment.
Additional objects, advantages, and novel features of the invention will become apparent to those skilled in the art upon examination of the following description or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained as particularly pointed out in the appended claims.